1. Field of the Invention
The present invention relates to a hammer drill functioning both as a hammer and as a drill and including a striking force transmitting mechanism for applying a striking force to a working tool, and a rotational force transmitting mechanism for transmitting a rotational force to the working tool.
2. Description of Related Art
Hammer drills provided with both a striking force transmitting mechanism and a rotational force transmitting mechanism have been conventionally provided with three operation modes: a rotation and strike mode for applying a striking force to the working tool while simultaneously driving the working tool to rotate, a rotation only mode for driving the working tool to rotate, and a strike only mode for applying a striking force to the working tool. This type of hammer drill requires an operation mode switching mechanism to switch the operation mode according to the desired operation.
One such operation mode switching mechanism has been proposed in U.S. Pat. No. 6,557,648 (corresponding to Japanese patent-application publication No. 2002-192481). This operation mode switching mechanism is provided with a gear and a clutch mechanism for each of the striking force transmitting mechanism and rotational force transmitting mechanism. In order to switch operation modes, the hammer drill uses the clutch mechanism to interrupt the transfer of a rotational force from a motor.